Machine for grinding drills



(No Model.)

T. R. PIOKERING.

MACHINE FOR GRINDING DRILLS. No. 282,364. Patented July 31,1883;

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UNITED STATES PATENT OF I E. 7

THOMAS R. PICKERING, OF PORTLAND, CONNECTICUT.

MACHINE FOR GRINDING .DRILLS.

SPECIFICATION formingpart of Letters Patent No. 282,364, dated July 31, 1883,

Application filed June 11, 1883. (No model.)

To all whom it may concern Be it known that I, THOMAS R. PIOKERING, of Portland, in the county of Middlesex and State of Connecticut, have invented new Improvement in Machines for Grinding Drills; and I do hereby declare the following, when taken in connection with accompanying drawings and the letters of reference marked thereon, to bea full, clear, and exact descrip-I tion of the same, andwhich said drawings constitute part of this specification, and represent, in

Figure 1, a perspective view; Fig. 2, a top or plan View, a portionbroken away to show the drill in the grinding position;'Fig.' 3, a face View of thegrinding-wheel, showing the drill in position andindicatingthe under-cut; Fig. 4, a face view of the rest H, showing the twist-drill thereon in section, enlarged.

This invention relates to an improvement in apparatus for sharpening drills for metalwork, with special reference to twist-drills, but applicable to flat drills.

In the machines usually employed for this work a holder is constructed to present the drill, generally, to the periphery of the grinding-wheel, in some cases to the flat face of a revolving grinding-wheel; but in such appara-' tus it is difficult, if not impossible,to produce an under-cut the most favorable to the best working of the drill, and such as readily pro duced by agrinder when he holds the drill in his hand,- but in such hand-grinding it is difficultto attain perfect or the same pitch upon both sides of the point.

The object of my invention is to construct an apparatus which will give an under-cut-to the drill substantially like that which may be produced by the operator when grinding by hand, and yet preserve the accuracy of mechanically holding the drill; and the invention consists, principally, in the employment of a hollow grinding-wheel, and combining therewith a holder which will present the drill upon the inner surface of the grinding -whcel, as more fully hereinafter described. I

A represents the bed of the machine; 13, the

bearing on which the driving-shaft C is arranged, power being communicated to said a ring,F, of the grinding material, the inner surface ofthering exposed. Upon the bed thedrilLholder is arranged. This holder, as

here-represented, consists of two slides, G H,

arranged between guides a a at an angle of about thirtydegrees to the plane of the grinding-wheel. The slide His made adjustable by I a leadingscrew, b, and the other slide is adjustable and held between the guides by a setscrew, cl, which may be set into different holes,

in the bed to secure it in the different positions in which it may be desirable to place it. The

top or upper end of the guides G H are fitted to receive the drill I, and the slide G is provided with an adj Listing-screw, e, in axial line with the drill, and so as to abut against the shank end of the drill as it lies in the guides. The turning of the adjusting-screw 6 will move the drill longitudinally on the slides according to the direction in which the'screw e is turned. The driving-shaft C is arranged in its bearings so that it may have a certain amount of axial or longitudinal movement, and in such axial movement will carry the head E with it. The drill is placed upon the guides and its end brought against the innen surface of the re volving grinding-ring and slightly below the central line of the grind ng-wheel. The grinder, revolving, cuts aw. y the metal of the drill until it is brought to a sharp edge upon the upper side and on t required angle, it being understood that the pper side of the drill, as

it thus stands, is th cutting-edge. Below this upper side or on ing-edge the under-cut is produced, because the drill stands below the central'line, and the incline or extent of undercut will depend upon the relative position of the drillthat is to say, the lower down the drill be arranged, the greater will be the undercut. One side having been ground, the

drill is turned over upon its rests to present the opposite side, and that side is ground in like manner with a certainty of the same inclination as the opposite side, and also of the same under-cut, the two angles coming tothe center in the usual manner of grinding drills.

111' the case of flat drills, there is no difficulty in properly presenting the drill to the grinding-surface. When grinding one side, it lies flat upon the rest, and, reversed, the other side also lies flat, and the two flat sides being in parallel planes the presentation of the drill is governed by those flat sides; but in the case of a twist-drill there is no such flat surface to govern the position of the drill.- In this class of drills the cutting-surface on each side must stand diagonally across the twist; hence, in grinding, the drill must be presented so that at the point of grinding the plane of the twist will be substantially parallel with the plane of the axis of the grinding-wheel.

The slide or rest H is constructed upon its upper end as shown, to embrace the twist of the drill, and so that, the drill held thereon, longitudinal movement imparted to the drill will cause a rotation of the drill corresponding to the convolutions of the twist; hence if the drill be held from rotation, and the slide Hbe moved in one direction or the other, it will correspondingly turn the drill upon its axis, and by such turning will bring the plane of the twist at the grinding-point into the proper relative position to the grinding surface. Therefore when a twist-drill is to be ground the operator places the drill upon the rests, as seen in Fig. 1, and if the twist be not in the proper relation to the grindingsurface he moves the'rest or slide H accordingly toward or from the point of the drill, which will turn the drill until the proper position is attained, and there will remain stationary. Then,when one side is ground, the drill is reversed and the opposite side ground. This arrangement and support of the drill insures the equal grinding upon opposite sides-that is to say, the drill having been ground upon one sideand then turned upon the opposite side, the operator bringing the twist on that side into the same plane as the first, the grinding is then made upon that side, and is sure to be to the same extent as upon the opposite side, making the two sides alike, and the point consequently central. The set-screw c is employed to insure the like presentation of the two sides, for if the drill abut against the screw on grinding one side, and then on grinding the other side it abut against the screw in like manner, then the same extent of grinding is insured upon both sides.

To produce the best work, it is desirable to move the grinding-wheel so as to travel over the surface being ground. It is for this reason that the driving-shaft is constructed for a certain amount of longitudinal movement, and this movement may be given by means of alever, L, engaged with the driving-shaft, as shown, sothat when the operator moves 1t in either direction it moves the grinding-wheel accordingly, and so that when the drill is set in position the grinding-wheel .may be moved forward and the inner surface pass over the .end of the drill and perform the grinding and then return. I

The head E is best madeby forming a recess in its face to receive the grinding-ring, and that ring placed in the recess and secured by setscrews, as shown, or otherwise. The grinding-ring may, however, be otherwise arranged, or may in itself constitute the head and be fixed directly to the shaft; but I prefer the ring for the reason that it is cheaply made, and one may be removed and replaced by another.

Instead of imparting axial movement to the driving-shaft, whereby the traveling of the grinding-surface over the end of the drill is produced, the driving-shaft may be without axial movement, and the holder'which carries the drill may have imparted to it a movement parallelwith the axis of the grinding-wheel, to

cause the end of the drill being ground to pass over the surface of the grinding-wheel.

I claim- 1. The combination of a ring-shaped revolving grinding-wheel and a holder arranged to present the end of the drill to be ground upon the inner surface of the said grinding-wheel, substantially as described.

2. The combination of the ring-shaped revolving grinding-wheel and a holder arranged to present the end of the drill to be ground upon the inner surface of the said grindingwheel, the said grinding-wheel also constructed for longitudinal or axial movement, substantially as described.

3. The combination of the ring-shaped re- \volving grinding-wheel and the rests G H, the

forward rest, H, made adjustable to properly present the end of the drill to the inner surface of the grinding wheel, substantially as described.

4. The combination of the ring-shaped revolving grinding-wheel and the rests G H, the rest Ginade adjustable and provided with the screw 6 in axial line with the drill when on the rest, substantially as described.

THOMAS E. PIOKERING.

Witnesses:

JNo. H. HALL, R. H. PASOALL. 

